- Author: Ben Faber
You see them here, you see them there, you see those brown garden snails everywhere in the avocado trees this year. A wet year. What do you expect? Lush, beautiful tree growth, yeah. And when you come to harvest the fruit, the leaves and fruit are covered with snails. They are in your hand as soon as you go to pick the fruit.
It's especially noticeable on trees with a tight canopy with poor air circulation and canopy skirts down to the ground. Young GEM trees with their tight canopies and fruit low down and even in the leaf mulch, are especially prone in a wet year like this. We don't normally expect to see snails in avocados. They seem to go for citrus whether it's a wet or a dry year and growers are aware of the need for snail monitoring and control. But avocado growers can get caught off guard.
Snail feeding on fruit
Snails love the closed canopy which is more humid with direct contact to access from soil
So what do you do?
- Inspect young and topworked trees regularly for damage, especially during and after wet conditions. Be sure to distinguish the cause of damage. Caterpillars, earwigs, Fuller rose beetle, grasshoppers, and June beetles also chew tree foliage.
- Inspect surfaces for slimy or dry silvery trails characteristic of snails and slugs. Look for snails hidden under trunk wraps or other shelters near trunks.
- Modify cultural practices, encourage biological control, and exclude snails from canopies to provide good control.
- Prune the skirts up so that they are not touching the ground, but not so high that leaf mulch is blown away.
- Control weeds in young groves and groves where tree canopies are sparse as low vegetation favors snails.
- Retain dropped leaves and apply coarse organic mulch near trunks to retard snail numbers and to suppress root rot and weeds. Frequent microsprinkler irrigation encourages snail problems.
- Increase the interval between irrigations to the extent compatible with good tree growth. Trim branches that touch soil to restrict snail access to canopies and expose the soil surface to drying.
Birds and other small vertebrates, parasitic flies, and several types of predatory beetles commonly prey on snails. The predatory decollate snail (Rumina decollata, family Subulinidae) is widely distributed in southern California. Decollate snail is commercially available and legal for introduction only in certain San Joaquin Valley and southern California counties (Fresno, Imperial, Kern, Los Angeles, Madera, Orange, Riverside, Santa Barbara, San Bernardino, San Diego, Ventura, and Tulare counties). Decollate introductions are not recommended in avocado. Establishment of significant decollate numbers usually requires several years after introduction, and brown garden snail primarily is a pest when avocado trees are young.
Snails and slugs are repelled by copper. Commercially available bands of copper foil wrapped around trunks exclude snails. Another alternative is to add Bordeaux mixture to whitewash and paint 1 to 2 inch strip around the trunks of trees. Certain snail baits are available for spot applications. Molluscicides also kill predatory decollate snails. Pesticides are rarely warranted for mollusk control in avocado.
Read more at UC IPM
https://ipm.ucanr.edu/agriculture/avocado/brown-garden-snail/#gsc.tab=0
- Author: Ben A Faber
Brooks Engelhardt of Natural Resources Conservation Service says:
Greetings,
We have an EQIP-Disaster (for recent storm damage) fund pool open for FSA declared disaster counties, which includes Ventura County. Application deadline is May 24, 2024. It covers irrigation equipment, vehicle access, animal waste structures and forestry improvement.
If you know of anyone interested, please have them contact me.
Brooks Engelhardt
District Conservationist
USDA, Natural Resources Conservation Service
Oxnard, CA
Cell phone: 760-217-9197
Office: 805-609-2959
- Author: Ben A Faber
Growers Invited to Avocado Lace Bug Presentation
On May 14 at 12:30 p.m., Paloma Dadlani — a graduate student under Dr. Mark Hoddle who has been spearheading avocado lace bug research funded by the California Avocado Commission — will deliver her master's thesis defense seminar. Interested California avocado growers can view the thesis defense online or attend in person at the UC Riverside Entomology Building located at 165 Citrus Drive, Riverside, CA.
The thesis covers the following topics:
- Effects of temperature on developmental and reproductive biology, and degree-day models. This work helps predict development times in the field and will inform growers on possible levels of control from hot weather events.
- Two years of population phenology data from four commercial Hass avocado orchards in San Diego County, and surveys for ALB on non-Hass avocados like GEM, Lamb Hass, Bacon, and Fuerte. Natural enemy surveys are included, and sticky card captures to monitor adult dispersal by flight.
- Updated molecular analyses on ALB populations in San Diego county (the original 2004 population in Chula Vista and National City are still there), including comparisons to the "aggressive" populations in northern San Diego County, Riverside, Los Angeles, and Santa Barbara Counties and the extremely damaging populations in Hawaii.
- Author: Ben A Faber
- Author: Ben Faber
Old crop, new crop. What's up there in the trees? Are they big enough to sell? Is there a good set for next year? These are questions every avocado grower has every year, and often all year long. What is up there in the trees is confounded by what is called the "Avocado Illusion".
And boy was I reminded of the issue the other day when harvesting a GEM planting density trial. You don't see GEMs, you feel them, sense them being somewhere near your hand. There's a mass that's different from all the leaves near your hand, and you reach for it with your clipper and by golly you got a live one. But how many have you missed? You really need to search.
In a Science Magazine Letters to the Editor in Dec 1990, Paul Sandorff commented on a book written by Maurice Hershenson called The Moon Illusion. In the book Hershenson described the illusion of why the moon seemed so much larger when it was on the horizon than when it rose to its zenith on the same night. http://science.sciencemag.org/content/250/4988/1646.1
Sandorff said that this illusion applied to avocados since it was so hard to gauge the size of avocados when they were in the tops of the tree canopy. It is the surrounding environment that puts a context to size according to this theory of illusion.
Hershenson added to this observation in the March 1991 Science letters section with the comment that the leaves surrounding the fruit changes our depth perception and so changes our idea of the fruit size.
A further addendum to the avocado illusion theory is that since the fruit are the same color as the leaves (they are both dark green and the fruit unlike most other fruit continues to photosynthesize), it is hard to actually make out the fruit. You can be looking right at the fruit and not see it, confusing it with a leaf.
This illusion makes for difficult fruit estimation. To compensate for this illusion, I will eye the canopy in quadrants, counting the number of fruit, then arbitrarily doubling that total number. It usually gives a pretty close number to the real number of fruit that are in the tree.
By the way, with all the low down fruit in the skirt and with the wet winter, there were a heck of a lot of snails in the canopy dining on fruit.
Photo:
Can you count the number of fruit in this Hass canopy?
Photo: a mess of GEM fruit revealed hiding in the skirt.